1. Field of the Invention
The present invention relates to an optical head device for use in recording and/or reproducing on and/or from an optical information recording medium, such as an optical disc, and to a recording and/or reproduction device provided with such optical head device.
2. Description of the Related Art
Commercially available high density and high capacity optical information recording media include optical discs such as DVDs, Blu-ray Discs (hereinafter referred to as BDs), and the like. The use of these optical discs have been increasing rapidly in recent years as recording media for recording images, music, computer data and the like. In response, developments have been made eagerly to realize smaller size and lighter weight of compatible optical head devices for recording and/or reproducing information on and/or from optical recording media of different standards such as BD, DVD, CD and the like.
Here, the laser beams for use in recording and reproducing on and from BDs, DVDs and CDs respectively have different wavelengths. Specifically, BDs use a laser beam having a wavelength of 405 nm, DVDs use a laser beam having a wavelength of 660 nm, and CDs use a laser beam having a wavelength of 785 nm. For an optical head device compatible with three wavelengths, an optical path is used both for the laser beam for use in recording and reproducing on and from CDs and DVDs and for the laser beam for use in recording and reproducing on and from BDs, and the components are used in common so as to reduce the number of components and to realize cost reduction.
For recording and/or reproducing on/from the CDs and DVDs, a material that strikes a balance between durability and high performance has already been developed with respect to the light having the wavelength for use in recording and reproducing on and from the CDs and DVDs. However, such optimal material for the CDs and DVDs does not necessarily have sufficient durability against the light of the blue wavelength range for use in recording and reproducing with respect to the BDs.
In fact, when such an optical component made of an optimal material for the CDs and DVDs is used in a three-wavelength compatible optical head device for CDs, DVDs, and BDs, it has discovered that the durability of the optical component, through which a light beam of the blue wavelength range for use in recording and reproducing with respect to the BDs may pass, is liable to deteriorate. Specifically, when adopting such optical component made of an optimal material for the CDs and DVDs, a problem arises in that its inherent durability and characteristics cannot be ensured in the three-wavelength compatible optical head device of CDs, DVDs, and BDs.
International Publication No. 2008/001636 describes a conventional example of a compatible optical head device provided with a light source which emits light in a blue wavelength range, which prevents deterioration of the durability of the optical component made of a material optimized for an optical path of the laser beam for use in recording and reproducing on and from CDs and DVDs. In this conventional example, an optical multilayer film is formed on an optical component such as a polarized hologram with a phase plate so as to prevent deterioration of the organic material used in the optical component by shielding blue stray light with the optical multilayer film even if such blue stray light is generated from the blue laser light as emitted from blue laser beam source.
However, it is extremely difficult to effectively prevent such material optimized for the CDs and DVDs from deteriorating when used for the three-wavelength compatible optical head device for CDs, DVDs, and BDs. In particular, it has been discovered that even with a small amount of light in the blue wavelength range, the objective lens made of resin, which is an essential component of the optical head device, may deteriorate.